1. Field of the Invention
The present invention relates to an imaging apparatus and a method of controlling the imaging apparatus. In particular, the invention relates to an imaging apparatus and a method of controlling the imaging apparatus capable of obtaining a through-the-lens image closer to an image at the time of captured-image storage.
2. Description of the Related Art
In recent years, in accordance with the spread of digital cameras, there have been widely used methods of displaying a taken image (a through-the-lens image), which is taken from an imaging element, on a monitor provided on a digital camera before captured-image storage for storing an image, which is obtained by capturing an image of a subject in the imaging element, in a storage unit.
Generally, with digital cameras, when a user presses a shutter button, at a predetermined timing (a captured-image storage timing) corresponding to the instruction, an image which is taken from the imaging element is stored as a captured image in a memory or the like. Through-the-lens image display is a function of displaying the image, which is taken from the imaging element, as a through-the-lens image on the monitor before the timing of the captured-image storage. The user determines the composition, timing, setting, and the like while checking the through-the-lens image, and performs captured-image storage (for example, presses the shutter button).
That is, such a through-the-lens image is an image for allowing a user to check the finish of the captured image before performing the captured-image storage. Accordingly, in the through-the-lens image, it is preferable to reproduce the finish of the captured image as accurately as possible.
For example, in order to reproduce a depth of field or the like through an aperture stop, it is necessary to display the through-the-lens image by using an aperture the same as an aperture at the time of the captured-image storage. In this case, it is necessary to adjust the aperture to an exposure which is appropriate in a state where the aperture is fixed. Hence, it is also necessary to change parameters for performing other exposure controls such as an exposure time and an ISO (International Organization for Standardization) sensitivity (gain).
However, under certain circumstances where some light sources are used, there is a concern about occurrence of a flickering phenomenon, which is referred to as flicker, in the through-the-lens image. For example, when an image of a subject is captured under a light source, which flickers at a predetermined frequency, such as a fluorescent light, in accordance with a frame rate or an exposure time thereof, the luminance of the subject temporally changes in the through-the-lens image. Accordingly, there is a concern about the flickering phenomenon caused by the change.
The finish of the through-the-lens image, in which such flicker occurs, becomes different from the captured image. Consequently, in the through-the-lens image in which the flicker occurs, it is difficult for a user to figure out the finish of the captured image.
For this reason, in order to suppress the occurrence of such flicker, there has been proposed a method of adjusting the frame rate of the camera in consideration of the frequency of a light source (for example, refer to Japanese Unexamined Patent Application Publication Nos. 11-155107 and 07-298130).
For example, there is a method of setting the shutter speeds (the exposure times) of the camera to discrete values so as to make the shutter speeds equal to the integer multiples of the frequency of the light source. In this case, the allowable ranges of parameters for controlling exposure are restricted. Therefore, there is a concern that the range of the luminance area in which the automatic exposure control is available may be restricted.
Moreover, for example as described above, when the user controls the aperture in order to adjust the depth of field, the number of controllable parameters decreases. Accordingly, there is a concern that the range of the luminance area in which the automatic exposure control is available may be more greatly restricted.
For this reason, there has been proposed a method of performing exposure control so as not to cause flicker before the captured-image storage and performing the exposure control regardless of occurrence of flicker at the time of the captured-image storage (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-74530).